Influence of bacterial biofilms on Bacillus globigii spore viability in model chlorinated water distribution systems

摘要

Viability of Bacillus globigii spores in chlorinated polyvinyl chloride (PVC) pipe loop systems werenexamined under oligotrophic conditions. Three 2.5cm ￡ 10m pipe loops having poised freenchlorine concentrations of 0.0, 0.5, and 1.0 mg/L were seeded with 3.0 ￡ 108 B. globigii sporesneach and viability was assessed over a 21 day period in both the recirculating waters and withinnthe biofilms associated with pipe wall surfaces. After 10 min of exposure, viable spores werenfound to be associated within the pipe biofilms. In the untreated pipe loop spore counts remainednstatistically consistent in both the bulk water and biofilm until 1.0 mg/L free chlorine wasnintroduced, then spores were completely inactivated in less than seven days. Spores within thenpipe loop poised at 0.5 mg/L free chlorine showed a 7.6-log10 inactivation in the bulk waternphase, but only a 2.7-log10 inactivation was observed within the biofilm after 14 days ofntreatment. Complete inactivation was observed in the 1.0 mg/L free chlorine system in both thenbiofilm and the bulk water phase in less than 10 min. These data demonstrated that B. globigiinspores were readily incorporated into PVC pipe biofilms, which decreased spore inactivationnnearly five orders of magnitude under moderate free chlorine concentrations.